In FY2019, we investigated the role played by human polymorphonuclear leukocytes (PMNs or neutrophils) in host defense against bacterial pathogens. Neutrophils are essential to the innate immune response against invading microorganisms. In contrast to the acquired immune response, which requires time to develop and is dependent on previous interaction with specific pathogens, the ability of PMNs to kill infectious microorganisms is immediate, non-specific, and not dependent on previous pathogen exposure. Inasmuch as PMNs produce toxic microbicidal components and are the predominant immune cell in most bacterial infections, moderation of infection-induced inflammation is critical for limiting host tissue destruction. A key aspect of our research investigates how PMNs ingest and kill bacteria, and elucidates post-phagocytosis sequelae such as apoptosis, processes crucial for the resolution phase of inflammation. These studies continue to provide fundamental insight into the resolution of infection in humans.